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from __future__ import annotations
from collections.abc import Sequence
from typing import Any, Optional
import numpy as np
from braket.circuits.operator import Operator
[docs]
class QuantumOperator(Operator):
"""A quantum operator is the definition of a quantum operation for a quantum device."""
def __init__(self, qubit_count: Optional[int], ascii_symbols: Sequence[str]):
"""Initializes a `QuantumOperator`.
Args:
qubit_count (Optional[int]): Number of qubits this quantum operator acts on.
If all instances of the operator act on the same number of qubits, this argument
should be ``None``, and ``fixed_qubit_count`` should be implemented to return
the qubit count; if ``fixed_qubit_count`` is implemented and an int is passed in,
it must equal ``fixed_qubit_count``, or instantiation will raise a ValueError.
An int must be passed in if instances can have a varying number of qubits,
in which case ``fixed_qubit_count`` should not be implemented,
ascii_symbols (Sequence[str]): ASCII string symbols for the quantum operator.
These are used when printing a diagram of circuits.
Length must be the same as `qubit_count`, and index ordering is expected
to correlate with target ordering on the instruction.
For instance, if CNOT instruction has the control qubit on the first index and
target qubit on the second index. Then ASCII symbols would have ["C", "X"] to
correlate a symbol with that index.
Raises:
TypeError: `qubit_count` is not an int
ValueError: `qubit_count` is less than 1, `ascii_symbols` are `None`,
``fixed_qubit_count`` is implemented and and not equal to ``qubit_count``,
or ``len(ascii_symbols) != qubit_count``
"""
fixed_qubit_count = self.fixed_qubit_count()
if fixed_qubit_count is NotImplemented:
self._qubit_count = qubit_count
elif qubit_count and qubit_count != fixed_qubit_count:
raise ValueError(
f"Provided qubit count {qubit_count}"
"does not equal fixed qubit count {fixed_qubit_count}"
)
else:
self._qubit_count = fixed_qubit_count
if not isinstance(self._qubit_count, int):
raise TypeError(f"qubit_count, {self._qubit_count}, must be an integer")
if self._qubit_count < 1:
raise ValueError(f"qubit_count, {self._qubit_count}, must be greater than zero")
if ascii_symbols is None:
raise ValueError("ascii_symbols must not be None")
if len(ascii_symbols) != self._qubit_count:
msg = (
f"ascii_symbols, {ascii_symbols},"
f" length must equal qubit_count, {self._qubit_count}"
)
raise ValueError(msg)
self._ascii_symbols = tuple(ascii_symbols)
[docs]
@staticmethod
def fixed_qubit_count() -> int:
"""Returns the number of qubits this quantum operator acts on,
if instances are guaranteed to act on the same number of qubits.
If different instances can act on a different number of qubits,
this method returns ``NotImplemented``.
Returns:
int: The number of qubits this quantum operator acts on.
"""
return NotImplemented
@property
def qubit_count(self) -> int:
"""int: The number of qubits this quantum operator acts on."""
return self._qubit_count
@property
def ascii_symbols(self) -> tuple[str, ...]:
"""tuple[str, ...]: Returns the ascii symbols for the quantum operator."""
return self._ascii_symbols
@property
def name(self) -> str:
"""Returns the name of the quantum operator
Returns:
str: The name of the quantum operator as a string
"""
return self.__class__.__name__
[docs]
def to_ir(self, *args: Any, **kwargs: Any) -> Any:
"""Returns IR representation of quantum operator.
Args:
*args (Any): Not Implemented.
**kwargs (Any): Not Implemented.
Raises:
NotImplementError: Not Implemented.
Returns:
Any: The the canonical intermediate representation of the operator.
"""
raise NotImplementedError("to_ir has not been implemented yet.")
[docs]
def to_matrix(self, *args: Any, **kwargs: Any) -> np.ndarray:
"""Returns a matrix representation of the quantum operator.
Args:
*args (Any): Not Implemented.
**kwargs (Any): Not Implemented.
Raises:
NotImplementError: Not Implemented.
Returns:
np.ndarray: A matrix representation of the quantum operator
"""
raise NotImplementedError("to_matrix has not been implemented yet.")
[docs]
def matrix_equivalence(self, other: QuantumOperator) -> bool:
"""Whether the matrix form of two quantum operators are equivalent
Args:
other (QuantumOperator): Quantum operator instance to compare this quantum operator to
Returns:
bool: If matrix forms of this quantum operator and the other quantum operator
are equivalent
"""
if not isinstance(other, QuantumOperator):
return False
try:
return np.allclose(self.to_matrix(), other.to_matrix())
except ValueError:
return False
def __repr__(self):
return f"{self.name}('qubit_count': {self.qubit_count})"